There has been a trend over the past several years to provide agricultural combines of greater threshing capacity. While the size of combines has been increased over earlier designs, there is a practical limit to physical increases in size of the crop cutting header portion of the combines.
The productivity of large capacity combines may be increased by operating at a higher ground speed, which requires a higher cutter speed. In the case of a reciprocating sickle type cutter, the inertia related forces in the cutter mechanism increase with the square of the frequency of reciprocation. The present invention is directed to providing a cutting mechanism which operates at high speed without imposing unduly high forces on its drive mechanism. An effort in this direction is the provision of a resonant cutting mechanism shown in a copending U.S. patent application Ser. No. 186,571 by Larry F. Stikeleather and Tony L. Kaminski filed Sept. 12, 1980 for Resonant Sickle Drive. In the resonant sickle drive of the before-mentioned patent application the resonant frequency of the cutting mechanism is within the reciprocating frequency range at which the sickle normally operates for crop cutting purposes. Operating the spring coupled sickle bar, at or near its resonant frequency, results in a greatly reduced input peak torque requirement. Also, the lower peak forces are expected to result in longer operating life of drive components.
Heretofore, others have suggested the use of multiple resilient spring devices for cushioning or for storing and releasing energy during reciprocation of a cutting device. Several such arrangements are shown in U.S. Pat. Nos. 273,341; 2,109,085; 3,538,690 and 3,624,990.